The objectives of this proposal will seek to develop and characterize a model system for the targeting of drugs to specific cells which have the potential for inducing tumors in mammals. The octapeptide toxin Alpha-amanitin will be chemically modified to permit its covalent conjugation to free amino groups on lectins displaying specific affinities for specific carbohydrate residues (Concanavalin A and castor bean lectin) and monoclonal antibodies directed against cell surface antigens (Thy-1.2 antigens on lymphoma cells and cell membrane antigens from M-3 fibrosarcoma cells. The conjugates will be characterized with respect to the nature of the amanitin-protein linkage, the number of amanitin moieties bound, and the inhibitory activity of the coupled amanitin toward calf thymus RNA polymerase II. Conjugates and Concanavalin A and castor bean lectin will be evaluated for their specific binding to and inhibitory potential against both lymphoma and sarcoma cells in culture and the protection of this inhibition by free lectins and specific carbohydrate ligands. Labeled conjugates (3H-amanitin, 125I-protein) will be utilized to determine the mechanism of endocytosis an processing of the conjugates under conditions which lead to specific cell inhibition. Amanitin-antilThy-1.2 conjugates will be prepared using monoclonal antiThy-1.2 antibody. These conjugates will be examined for their inhibitory potential against murine lymphoma's EL4 (Thy-1.2+) and C1498 (Thy-1.2-) in syngeneic C57BL/6 mice. In addition, these conjugates will be similarly evaluated against S49.1 (thy-1.2+) and S49 (Thy-), a mutant derived from 49.1 but lacking Thy-1.2, in syngeneic BALB/c mice. In both cases the ability to increase the survival time of the host. Amanitin conjugates to monoclonal antibodies directed against M-3 fibrosarcoma cell membrane antigens will be prepared using an established hybridoma. The inhibitory activity of these conjugates against cell proliferation in vitro and in vivo will be determined. The in vivo studies will compare the potential of the conjugate to block localized solid tumor in mice inoculated in the foot pad and to protect mice against generalized solid tumor deposition when inoculated through intraperitoneal injection.